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Full text of "Tests with sprays for controlling grasshoppers on farm lands in North Dakota and Texas, 1950-51"

LIBRARY 

September 1952 E-845 



United States Department of Agriculture 

Agricultural Research Administration 

Bureau of Entomology and Plant Quarantine 



TESTS WITH SPRAYS FOR CONTROLLING GRASSHOPPERS 
ON FARM LANDS IN NORTH DAKOTA AND TEXAS, 1950-51-1/ 

By R. L. Shotwell 
Division of Cereal and Forage Insect Investigations 



Farm-scale tests of aldrin sprays and a single chlordane spray for the 
control of grasshoppers were made in 1950 in Bottineau County, N. Dak., 
and of aldrin, dieldrin, and toxaphene sprays in 1951 on the Bluebonnet 
Farm at McGregor, Tex. Bottineau County is in the extreme north-central 
part of North Dakota and is over 1,200 miles, or 16 degrees latitude, north 
of McGregor, which is in McLennan County in central Texas. The difference 
in climate between the two localities is indicated from the following data 
which are averages of records taken over 39 or 40 years. 

Bottineau, N. Dak. 

Average temperature (°F.) 

January ----------- 1.5 

July 67.7 

Annual rainfall (inches) ---- 15.81 

Growing season (days)- - - - - 112 

Small grains and flax are the principal crops raised in Bottineau 
County, and corn and cotton in central Texas where the Bluebonnet Farm 
is located. Melanoplus mexicanus (Sauss.) and bivittatus (Say) are the 
important grasshopper species in the former and differentialis (Thos.), 
in the latter locality. 

Such a diversity of farming and climate offered an excellent oppor- 
tunity for studying the effect of insecticide sprays on grasshoppers under 
widely different conditions. 



Waco, 


Tex. 


48. 


6 


85. 


7 


34.90 


250 





1/ This work was done in cooperation with the Division of Grasshopper 
Control of this Bureau and the Texas Agricultural Experiment Station, 
A. and M. College System of Texas. In North Dakota valuable assistance 
was rendered by farmers, the county agent of Bottineau County, members 
of the Federal Soil Conservation Service at Bottineau, and one commercial 
plane operator. 



-2- 



MATERIALS AND METHODS 

The sprays used in Texas were prepared from ready made concen- 
trates containing 6 pounds of aldrin or toxaphene or 2 pounds of dieldrin 
per gallon. Those used in North Dakota were made from concentrates 
containing either 2 pounds of aldrin or 8 pounds of chlordane per gallon. 
All the concentrates, except the aldrin used in Texas, contained an emul- 
sifier. They were diluted in oil or water to suit available spraying 
equipment. 

The dosages used at first were those that have generally given the 
best results- -namely, aldrin 2 ounces, dieldrin 1 ounce, chlordane 

1 pound, and toxaphene 1 1/2 pounds per acre. Late in the season, when 
the vegetation is taller and much less succulent or when barriers against 
migrating grasshoppers are set up to last 10 days or more, 3 to 4 ounces 
of aldrin, 2 ounces of dieldrin, 2 to 3 pounds of toxaphene, and 1 1/2 to 

2 pounds of chlordane per acre have been used for more effective control. 

The emulsion sprays were applied with a mist blower on a truck, a 
side-delivery nozzle being used. When driven at 7 and 10 miles per hour, 
this machine applied the spray in a swath 2 rods wide at the respective 
rates of 7 and 6 gallons per acre. In Texas in 1951 the blower was 
equipped with a USDA broadcast nozzle to apply the oil spray at a truck 
speed of 7 miles per hour, and the rate of application was 1 1/4 gallons 
per acre. 

Where ground sprayers were used, they were calibrated to give the 
required dosage on the basis of the average maximum speed the truck 
could travel over an infested, area. At this speed the entire area received 
the required dosage with a minimum waste of the insecticide. However, 
at reduced speeds, there were temporary increases in the rate of appli- 
cation, so that the total quantity applied exceeded the calculated dosage. 

In all the aerial spraying in North Dakota in 1950, oil sprays were 
used at the rate of 1 gallon per acre. When applied by plane the average 
dosage of the insecticide closely approximated that calculated. 

Before an infestation was treated, estimates were made of the grass- 
hopper population and damage. The species present and their stages of 
development were also noted. After treatment a check was made every 
day or two to determine the effects of the spray and the need for further 
treatment. At various times grasshoppers were collected to establish 
the current hatching period, in order to provide additional data on the 
seasonal history of the important species. 

TESTS IN BOTTINEAU COUNTY, N. DAK. 

A 4-section block of farm land and fields on 25 farms in Bottineau 
County were utilized for testing aldrin and chlordane in 1950. Two 
farms south across the line in McHenry County were also used. The 



-3- 



block of farm land was 4 miles east of Maxbass and was called the 
Maxbass spray area. A quarter section on one farm 3 miles west of 
Westhope, where some special work was done, was called the Westhope 
spray area. Maps of these areas are shown in figure 1. 

Much of the farm land in the county is in large blocks of 40 to 160 
acres. In some of the sandy areas strip cropping is practiced to prevent 
soil blowing. Besides small grains an extensive flax acreage was planted 
in 1950. 

Strip farming spreads grasshopper infestations throughout the field, 
as the strips of grain stubble after harvest become the egg beds of future 
infestations. These strips lie over the winter as stubble and the following 
summer are worked whenever the weather or the farmer's convenience 
permits. When worked, they are cultivated with a one-way disk which 
leaves the stubble and trash on the surface and the grasshopper eggs in 
about the same depth in the soil. Instead of preventing the eggs from 
hatching, disking hastens the process by leaving the surface bare of 
vegetation and largely unshaded. Past observations have shown the 
temperature of unshaded soil at egg depth, 1 to 2 inches below the sur- 
face, to be 10° F. higher than that of the shaded soil and that all the 
eggs hatch in the former but not in the latter situation. Cultivation also 
speeds the subsequent movement of young grasshoppers into nearby crops 
by destroying their food plants in the fallowed pieces of land. The strips 
are usually 10 rods wide, and the cropped strip is accessible to infesta- 
tion for its full length on both sides. 

On the other hand, block farming reduces the infestation to field 
margins, if the weeds or other food plants are kept down on fields being 
fallowed. The length of the margin is 2 miles for a 160-acre field and 
1 mile for a 40-acre field. For strip farming this length is 17 miles for 
a 160-acre field and 4 1/2 miles for a 40-acre field. 

By June 1, 1950, all farming in this part of North Dakota was at 
least a month late, owing to an unusually cold, snowy spring. When the 
deep snowcap covering the county finally melted late in May, every 
quarter section had its pot hole, or wet spot, until late in June, if not 
all summer. Small grain and flax were not harvested until late in 
September and October. 

Melanoplus mexicanus and bivittatus were late in their seasonal 
development. Hatching began on June 4 and ended on July 24. Further- 
more, it was estimated that, on the basis of the number of grasshopper 
eggs deposited in the fall of 1949, two-thirds of the threat to crops was 
dissipated by the spring and summer weather of 1950. 



48.5 


53.5 


36.6 


6.7 


9.1 


4.6 


- 


17.3 


- 


1.5 


- 


1.5 


5.8 


- 


- 


6.1 


- 


4.3 


- 


1.8 


- 


1.8 


- 


.9 



4- 



The percentage composition of the grasshopper populations was as 
follows: 

In crops In pasture 

Melanoplus mexicanus (Sauss.) 

bivittatus (Say) 

femur -rubrum (Deg.) 

packardii Scudd. 

dawsoni (Scudd.) 

angustipennis (Dodge) 
Other species 

Chorthippus longicornis (Latr.) 
Ageneotettix deorum (Scudd.) 
Phoetaliotes nebrascensis (Thos.) 
Spharagemon collare (Scudd.) 
Camnula pellucida (Scudd.) 

On the Maxbass and Westhope spray areas the objective was to elim- 
inate all grasshopper infestations, whereas on the 27 separate farms the 
problem was to eliminate all the grasshoppers threatening a particular 
field crop. Flax was threatened on all but two of these farms. 

Grasshoppers damage flax by defoliating it and cutting off the bolls 
as the seed matures. Since yields as high as 20 bushels per acre will 
gross up to $60 per acre at the current price, flax is a high cash crop. 
In 1949 toxaphene as a spray had given variable and unsatisfactory re- 
sults in flax in this area when applied at the rate of 1 1/2 pounds per acre. 
Consequently, a study was warranted to determine the value of aldrin 
sprays under similar conditions. 

Results on the Maxbass Spray Area 

The Maxbass spray area was in a sandy "blow-dirt" district having a 
long history of grasshopper damage. The crops were small grains, 
sorghums, corn, flax, and alfalfa. Part of the cropland was farmed in 
strips; the rest of the area was in hay, pasture, and weedy wasteland, 
as shown in figure 1. Fallow and planted strips are shown only where 
extensive spraying was done. The areas marked "cropland" needed no 
control. If the fallow strips had been worked at the time of spraying, 
the planted strips had to be sprayed. If not, the stubble and not the 
planted strips had to be treated. 

Table 1 summarizes the results of the spraying operations. Except 
for the 20-acre flax field, NE 1/4 of section 12, treated with 20 pounds of 
chlordane, all infestations were sprayed with aldrin in either oil or 
emulsion at the calibrated rate of 2 ounces per acre. The actual dosages 
of the aldrin varied slightly from this rate, as shown in the table. 



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-6 - 



A mist blower was used to apply the emulsion on 440.4 acres of 
weedy stubble or grain strips, weed patches, and margins. The side- 
delivery nozzle made it possible to cover the 10-rod wide strips by 
spraying from both sides and in both directions from the dead furrow in 
the middle without knocking down much grain. Some strips were so 
narrow that they could be covered by spraying only from the sides, pro- 
vided the wind was not blowing. A boom sprayer, tractor-drawn, would 
have knocked down 5 to 10 percent of the small grain and been of little 
use in the weedy areas. A plane was used to apply an oil spray of aldrin 
on 199 acres of weeds and chlordane on the 20 acres of flax. Most of the 
area was sprayed between July 24 and 29 during clear, warm weather 
with no wind. Figure 3 shows the weather conditions during this period. 

Populations of grasshoppers before the spraying averaged 20 to 30 
per square yard in the strips of grain and stubble and 30 to 300 in the 
margins. They were mostly mexicanus and bivittatus in all stages of 
development but principally in the third and fourth instars. 

Earlier on June 24, a 5 -acre portion of a stubble strip on high ground 
in the center of the SE 1/4 of section 12 was sprayed with aldrin at the 
average rate of 1 1/2 ounces per acre. An infestation of 300 newly hatched 
nymphs per square yard at the time of treatment was reduced 80 percent, 
but hatching continued until July 20. The residual effect was noticeable up 
to July 3, or 9 days after application. The strip was sprayed again on 
July 26. 

The outstanding spray job was that done on the weedy SW 1/4 of 
section 13 with a plane on July 18. This 160 -acre infestation numbered 
30 to 300 grasshoppers per square yard in a weedy cover 2 to 5 feet high. 
Of this tract 40 acres was a solid stand of sweetclover 4 to 5 feet high. 
Tall weeds and rough wet ground made it impossible to use the mist 
blower. The grasshoppers had commenced moving into and damaging 
crops adjacent to the quarter on four sides. An extra spray swath along 
the margins of these crops was laid down when the quarter was treated. 

The aldrin on this quarter section was applied at the rate of 2 ounces 
in 1 gallon of oil per acre by a Cub J- 3 plane equipped with a 40 -gallon 
sprayer. The pilot flew 6 feet above the weeds. The landing strip was 
4 miles from the field. It took 4 trips and 80 minutes, 6:40 to 8:00 p.m., 
to spray the 160 acres. In contrast, the best time with the mist blower 
mounted on a truck was 258 acres in 16 hours. 

After 24 hours 90 percent of the grasshoppers were dead, and 48 
hours later only occasional live grasshoppers were seen along the west 
and south section roads. Here some sick and freshly dead adults were 
observed on August 11, or 33 days after the quarter was sprayed. 

In like manner a heavy infestation in 39 acres of weeds in the NW 1/4 
of section 13 was wiped out on July 29. On August 21 an infestation of 
adults, 15 per square yard, in the 40-acre flax field, SE 1/4 of section 13 



- 7- 



was sprayed by plane with 2 ounces of aldrin per acre. Bolls of flax 
were already being cut off by the grasshoppers. Mortalities were 
apparent 2 hours after the application and the infestation was wiped 
out in 2 days. 

Over the entire four sections infestations were reduced to almost 
zero and 110 acres of flax saved from damage. The egg infestation was 
reduced from 1.15 pods per square foot in the spring to 0.09 pod in the 
fall (table 1). However, similar reductions were found in quarter sections 
or parts thereof not treated. Infestations did not develop in these places 
and no spraying was necessary. Much of the area was low, wet ground 
and some of the eggs did not hatch. Others hatched at times when in- 
clement weather destroyed the newly hatched nymphs. Approximately 
700 acres of the original 1,100 acres of infestation had to be sprayed. 
Although there is no proof that the reduction of infestation was due 
entirely to the spraying, the fall egg infestation might have been greater 
than the spring if no spraying had been done. The spraying removed 
any chance of grasshoppers being left to deposit e^gs. 

On July 25, 1951, a follow-up survey was made of the area. The 
grasshopper population numbered less than 1 per square yard for the 
entire four sections. Two farmers in the area said that they had not 
seen any grasshoppers that summer. 

Results on the Westhope Spray Area 

The NW 1/4 of section 31, shown in the upper right hand corner of 
figure 1, is part of a farm 3 miles west of Westhope. Between June 19 
and July 22, 12 acres of shelter belt, 32 acres of alfalfa, and 27 acres 
of pasture within the quarter were sprayed with 138 ounces of aldrin 
with the mist blower. 

Shelter belts of various kinds of trees and shrubs are common in this 
district and are sources of grasshopper infestations. On June 20, 25 
percent of the grasshoppers had hatched along the eastern half of the 
shelter belt running east and west through the middle of the quarter. 
The population numbered 200 per square yard, consisting of first, 
second, and third instars of mexicanus, bivittatus , Dissosteira 
Carolina (L.), and Camnula pellucida (Scudd.). One spray application 
at the rate of 2.8 ounces of aldrin per acre reduced this number to almost 
zero and held it there until July 6. 

During these 16 days only newly hatched nymphs were observed, and 
they continued to sicken and die. Between July 6 and 13 newly hatched 
grasshoppers survived and a new infestation developed. A second treat- 
ment with aldrin at 2 ounces per acre wiped out the infestation. 

Some of the best results, even in inclement weather, were obtained 
in the shelter belts where the growth of grass and weeds was heavy. 
There was no hurry about spraying these places, because the nymphs 



-8- 



remained in or close to the shelter belt long enough for the main hatch 
to take place. 

On July 13, 16 acres in the middle of the 32 -acre alfalfa field were 
sprayed with aldrin at the rate of 1 ounce per acre. The other 16 acres 
forming the east and west sides of the field were treated with 2 ounces 
per acre. The alfalfa was 4 to 8 inches high and had been cut once. The 
infestation in the alfalfa numbered 30 grasshoppers per square yard and 
in the bordering shelter belts, 60 per square yard. 

Five days later the middle 16 acres showed a reduction in numbers 
of 65 percent and the side strips 80 percent. By August 1 the middle 
strip had a population of 3 grasshoppers per square yard, while the side 
strips had 1 per square yard. In the alfalfa the egg pods before hatching 
had averaged 2 per square foot, but not a single pod was found in either the 
alfalfa or bordering shelter belts in the October egg survey. 

The 22-acre pasture in the northwest corner of the quarter section 
was also sprayed on July 13, at the rate of 1.3 ounces of aldrin per acre. 
The grass was 3 to 4 inches high and contained some weeds and short 
sweetclover plants. Before the spraying the grasshoppers numbered 
30 per square yard. In 5 days there were still 18 grasshoppers per 
square yard concentrated in 7 acres of the eastern side. This pasture 
was sprayed again on July 22 with 2 ounces of aldrin per acre. By 
August 1 the average population was 3 grasshoppers per square yard. 
Two similar sprayings were made on the small pasture east of the flax 
field. 

As shown in figure 1, the 15-acre flax field was bordered on three 
sides by treated shelter belts, pastures, and the alfalfa. The grass- 
hoppers did no damage to the flax and the infestations were reduced to 
noneconomic importance. No infestations developed on this place in 1951. 

Cool, rainy weather from June 20 to July 22 prevented the grass- 
hoppers from being active, and quick, decisive results with heavy mor- 
talities from the spraying were not obtained, as they were later else- 
where when the weather became warmer and drier and the grasshoppers 
showed greater activity. 

Ground Sprays to Protect Flax and Other Crops 

Besides the work done on the Maxbass and Westhope spray areas, 
ground spraying was done on nearby farms to eliminate threatening in- 
festations. On two farms the mist blower was used. 

On one of these farms an 80-acre sweetclover field bordered the full 
3/10-mile length of a 35-acre flax field. Two-thirds of the sweetclover 
had been cut for hay, and a leafless stubble remained. The other third, 
which was next to the flax, was left for seed and stood shoulder high. 
Grasshoppers numbered 80 per square yard in the stubble field and 300 
in the margins. In previous tests where toxaphene was used in sweetclover 



stubble, some difficulty was encountered in trying to control grass- 
hoppers with the recommended dosage. This field offered an oppor- 
tunity for testing aldrin under such conditions. 

Spray containing 3 ounces of aldrin per acre was applied on the 
afternoon of July 28 and the morning of July 29. Early on the morning 
of July 30, 1.37 inches of rain fell in the area, and again on July 31, there 
was 0.56 inch of rain. On August 1 the grasshoppers numbered 10 per 
square yard in the stubble and 5 in the standing sweetclover. By 
August 19 these numbers were further reduced to 4 per square yard in 
the stubble and fencerows and 1 in the uncut sweetclover. The farmer 
reported a marked residual effect for 9 days after the spray was applied 
in spite of the heavy rains. There was no grasshopper damage to the 
flax. In the fall survey the egg pods numbered 0.2 per square foot in 
the sweetclover field and its margins. 

The second ground spray test was made on July 27. Aldrin was 
applied at the rate of 3 ounces per acre on a 60-acre weedy wheatfield 
farmed in strips of fallow and wheat that was headed out. The population 
of 50 grasshoppers per square yard, made up of third, fourth, and fifth 
instars of mexicanus and bivittatus , was reduced to zero by August 19. 
Since this second farm was within 3 miles of the first, it was subjected 
to the same heavy rains on July 30 and 31 but without any apparent effect 
on the results. 

Aerial Sprays to Protect Flax 

Cooperative tests were conducted on 24 farms in Bottineau County 
where both aldrin and chlordane in oil sprays were applied by plane. 
A local plane operator did the spraying and furnished the oil at a cost 
of $1.15 per acre to the farmer. The Bureau of Entomology and Plant 
Quarantine furnished the insecticides. The plane was a Cub J-3 with 
the wing tips cut off square to prevent the spray from boiling up over 
the tips of the wings. The sprayer had a 40 -gallon capacity. The plane 
was flown within 6 feet of the crop and this movement forced the spray 
down into the plant cover in a rolling fog. 

Where a power or telephone line was along the edge of a field, the 
pilot first paralleled the line to the windward at about 15 to 20 feet 
elevation. This position allowed the spray to drift under the line and 
cover whatever margin there was along the edge. He flew the same 
swath again at 6 feet elevation to spray directly beneath the plane. If 
the rest of the field had to be sprayed in swaths perpendicular to the 
power or telephone line, he then continued to parallel the line for two 
or three more swaths into the field to make sure that that end of the 
field was adequately treated. 

On the 24 farms a total of 630 acres of flax and 237 acres of alfalfa, 
sweetclover, small grains, and margins were sprayed with aldrin at the 



-10- 

average rate of 2.2 ounces per acre. Chlordane at 1 pound per acre was 
applied on 173 acres of flax and 71 acres of other crops. All this 
spraying was done to protect 900 acres of flax. 

Infestations in the fields averaged 35 and in their margins 115 grass- 
hoppers per square yard. These numbers were all reduced to less than 
1 per square yard as a result of the spraying. 

Before the spraying the damage to the flax, measured by the number 
of bolls on the ground, averaged 10 percent and was as high as 35 percent, 
The treatments stopped further damage and prevented severe-to-total 
losses. 

The fields were treated between July 27 and September 9, so that the 
early spraying was done when the flax was in the late -bloom stage and 
the grasshoppers were late nymphs. At the time of the late spraying 
the flax was in the ripened-boll stage and all the grasshoppers were 
adults. The dosage of insecticide was not changed during the period, 
and there was no difference in the results between the early and late 
spraying. In six of the flax fields aldrin and chlordane were tested side 
by side with like results. 

Among the spray operations on the 24 farms there were several that 
warrant special discussion. On one farm a 17-acre field of barley in 
the dough stage with an infestation of 150 grasshoppers per square yard 
was adjacent to a flax field that was also heavily infested. All the leaves 
of the barley had been stripped off and some damage to the heads was in 
progress. One application of aldrin on the barley and on the flax reduced 
the infestation to less than 1 grasshopper per square yard in 5 days, and 
no eggs were deposited. 

On another farm a population of 75 grasshoppers per square yard in 
a 44-acre alfalfa field threatened not only the alfalfa but also a 60 -acre 
flax field adjacent to it. This infestation was reduced to almost zero 
by one application of aldrin to the alfalfa, and both crops were protected. 

On one farm there was a weedy roadway 3/4 mile long with a strip 
of rye 5 rods wide along the north edge, comprising 14 acres altogether. 
This area was heavily infested with an average of 300 grasshoppers per 
square yard. The infestation bordered the ends of flax and small-grain 
strips to the south. One spraying on July 27, before any of the grass- 
hoppers had moved more than 2 rods into these strips, wiped out all 
the infestation and prevented damage to the flax and small grain. This 
is a good illustration of what can be accomplished by treating marginal 
infestations while they are still concentrated on a few acres. 

Another example was a quarter section containing 80 acres each in 
flax and sweetclover, shoulder high, infested with 25 adult grasshoppers 
per square yard. Ten percent of the flax was damaged. One applica- 
tion of aldrin over the entire quarter section wiped out the infestation 
in both crops. The results were so unbelievable to the owner that he 
walked diagonally across the 160 acres and then from one side to the 



- 11 - 

other to check on them. He did not see one live grasshopper, and only 
by counting the dead ones on the ground could he convince himself that 
the spray had actually eliminated the infestation. 

Rains up to 1 1/2 inches fell during the spraying operations on the 24 
farms. Hardly a treatment escaped the rain, and it frequently fell 
within a few hours after the insecticide was applied. However, only one 
application was necessary to reduce the infestation to zero. 

Grasshopper damage up to 30 percent can occur in flax without being 
seen from the road or attracting the attention of the farmer. A closer 
examination to count the bolls on the ground is needed to show the severity 
of the damage. 

Most of such crop loss can be prevented by spraying. The first spray 
should be applied early enough to eliminate all newly hatched grass- 
hoppers in or near the flax, and a second to prevent reinfsstation from 
some outside source. In 1950 the flax yielded as much as 20 bushels per 
acre in the general area of North Dakota where the tests were made, 
which meant up to $62 per acre at the current price. The average 10- 
percent loss encountered during late spraying amounted to as much as 
$6.20 per acre, which would justify an early spraying and a second 
spraying if necessary. The early spraying is usually done on a greatly 
reduced acreage and the probable over-all cost of treatment is about $1.50 
per acre. 

In north-central North Dakota commercial airplane spraying has met 
with greater acceptance than the farmers' own use of ground equipment. 
There are several reasons why. Tractor-propelled boom sprayers knock 
down 5 to 10 percent of a small-grain crop if the grain is tall when treated. 
The worst grasshopper infestations are often concentrated in weedy places, 
where the ground is too rough or too wet for the use of ground equipment. 
Muddy fields also delay ground spraying. In a cultivated area spraying 
with a light plane is 5 to 10 times faster than ground spraying. The pres- 
sure of other farm work and the problem of calibrating a ground sprayer 
for different formulations of a single insecticide are added reasons why 
farmers would rather phone a good commercial operator to spray his grass 
hoppers than do it himself. 

TESTS ON THE BLUEBONNET FARM, TEX. 

The Bluebonnet Farm is a 17, 483 -acre tract of land obtained from the 
War Assets Administration by the Texas A. and M. College for conducting 
agricultural and livestock research and education. Figure 2 is a map of 
the farm, showing the locations of the 29 tests of aldrin and other sprays 
made in 1951. That was the fourth year of reclaiming this land, which had 
become heavily infested with Johnsongrass and grasshoppers, mainly 
differentialis , during the wartime period when it had been utilized as an 
ordnance plant. Most of the grasshoppers had been eliminated by vigorous 



- 12- 

control measures over a period of 3 years. Enough infestation remained, 
however, for spray tests in which aldrin, dieldrin, and toxaphene were 
used. 

The main objective of grasshopper control in this district is to protect 
cotton and other crops from differentialis, which hatches in the field 
margins and permanent pastures. 

The new organic insecticides, mainly toxaphene spray, have sup- 
planted the bran-sawdust bait as a control measure. Although good 
results had been obtained earlier in the season against grasshopper 
nymphs in green vegetation, the insecticides lost much of their effec- 
tiveness when hot, dry weather set in, the vegetation dried up, and the 
grasshoppers became adult. The main purpose of the 1951 work, there- 
fore, was to determine what could be done about this loss of effectiveness. 

The plan was to start spray operations and observations early and 
continue them into the season when hot weather could affect the results. 
Special efforts were then to be made to obtain the same good results 
produced in the early spraying, and also to determine the factors involved 
in the break-down of effectiveness. The general plan used was the same 
as in other farm-scale tests. Grasshoppers were collected from 'ime to 
time to determine the composition and progress of the infestations. 

In some tests two compounds or oil and emulsion sprays were used 
together. 

Results of Early Spraying 

The results of the early sprayings are shown in table 2 for each type 
of area sprayed. On 771 acres, 2,238 ounces of aldrin reduced populations 
of 12 to 77 grasshoppers per square yard to practically zero. In all but 
two tests, Nos. 10 and 19, this reduction was accomplished with one 
application in weeds and grass 4 to 24 inches high. In these tests the 
first application reduced the original numbers 85 and 25 percent, re- 
spectively. A second heavier application in each test reduced the re- 
maining infestations to zero. 

Grasshoppers were collected on the Bluebonnet Farm before the 
spraying, and in areas Nos. 10 and 19 again after one application of 
aldrin to determine what species persisted. The species collected are 
shown in table 3. Melanoplus differentialis was the dominant species 
before the spraying, but Hespereotettix viridis (Thos ) and Paraidemona 
mimica Scudd. (a wingless grasshopper) became the dominant ones after 
the aldrin spray had killed large numbers of differentialis . 

Although the sprayer was calibrated to deliver 2 ounces of aldrin 
per acre at a truck speed of 7 m.p.h., the average dosage in the early 
spraying was 2.9 ounces per acre. Much of the pasture was in rough, 
brushy bottom land, where travel was slower than planned for. This 
condition and failure to shut off the nozzle on frequent turns accounted 
for most of the heavy dosage. 



13- 



Table 2. --Field tests with aldrin, dieldrin, and toxaphene sprays for controlling grasshoppers in 1951, 
Bluebonnet Farm, McGregor,Tex. Emulsion concentrates used unless indicated otherwise. 



Insecticide 


Period of 
operation 


Area sprayed 


Insecticide used 


Grasshoppers per 
square yard 


and test No. 


Type 


Amount 


Total 


Average 
per acre 


Before 
spraying 


End of 
test 



Acres Ounces Ounces 



Number Number 









Ear 


ly Spraying 










Aldrin: 


















1, 7,9 


May 3- 


18 


Margin 
Roadway- 
Weed pateh-i/ 


48 


112 


2.3 


60 





5, 19 


10- 


24 


21 


60 


2.9 


77 





10 


21- 


29 


32 


126 


3.9 


40 





122/ 


22 




do. 


7 


16 


2.3 


60 





16 


28 




R. R. grade 


30 


70 


2.3 


12 





17 


29 




Fencerow 


8 


20 


2.5 


15 





2, 6, 8, 11, 


















14a, 15, 18 
4,2/132/ 


8- 


June 19 


Pasture 


584 1 


,742 


3.0 


58 


1- 


10- 


23 


do. 


41 


92 


2.2 


45 





Dieldrin: 


















20, 21, 22 


June 14 


-18 


Margins 


42 


63 


1.5 


49 





23 


18 




Fencerow 


24 


30 


1.2 


30 











Sweetclover 


37 


40 


1.1 


25 





Toxaphene: 


















3, 14b 
14c^ 


May 8 


-22 


Pasture 


18 


29 


1.6 


49 





22 




do. 


16 


24 


1.5 


40 











Late Spraying 










Aldrin: 


















25 


July 13 




Weeds 


14 


28 


2.0 


15 


12 




16 




do. 


14 


112 


8.0 


12 


1- 


26 


6 




Koadway 


17 


34 


2.0 


25 


10 


29^ 


14 




do. 


17 


84 


4.9 


10 


6 


17 




do. 


21 


126 


6.0 


6 


1 




17 




Pasture 


7 


21 


3.0 


12 


1 










16 


96 


6.0 


12 


1- 


Dieldrin: 


















24 


July 13 




Cotton 


14 


14 


1.0 


10 


7 




16 




do. 


17 


48 


2.8 


7 


1- 


28 


16 




Grass 


10 


28 


2.8 


5 


1- 


Toxaphene: 


















27 


July 16 




Cotton 


20 


30 


1.5 


8 


3 








Grass 


6 


18 


3.0 


7 


1- 


1/ Weedy p 


laces that had to b 


e sprayed twice 


before the 


infesta 


tion was r 


arinreH in •? 


.pm Spp ln«;t 



~i .. v.v.vjj, H xa^co mai udu lu ue sprayeu twice Deiore tne miestation w; 
column of table 3 for the species that persisted after the first treatment. 



2/ Insecticide was mixed with oil. 



STATE 



!g5JFBOJ*D 



14- 



Table 3. --Percentages of various species of grasshoppers collected in the 
habitats included in spray operations, Bluebonnet Farm, McGregor, 
Tex., 1951 



Species 



Road- 
way 



Margins 
of cotton 



•r, . ' Weedy area 
Pasture. ,. J 

after spraying 



Ageneotettix deorurn (Scudd.) 3.2 0.3 1.6 6.9 

Boopedon gracile Rehn 10.8 

Hesperotettix speciosus (Scudd.) 10.3 .7 6.5 9.9 

Hesperotettix viridis (Thos.) .8 1.1 19.7 

Melanoplus confusus Scudd. .10 

Melanoplus differentialis (Thos.) 84.7 95.9 67.4 19.0 

Mermiria maculipennis Bruner .5 2.8 4 4 

Oedipodinae species 2.7 

Paraidemona mimica Scudd. 4.4 38.1 

Phoetaliotes nebrascensis (Thos.) .9 

Unidentified .4 .3 .6 2.4 

Number of specimens collected 1,109 288 1,604 422 



In the early spraying the known residual action of the aldrin lasted 
up to 15 days. However, it was difficult to determine the residual 
effectiveness when most of the original infestation was wiped out in 3 
or 4 days by the'one application. 

About 60 percent of the area sprayed early with aldrin was made up 
of pastures and margins adjacent to a cotton crop not over 8 inches high. 
The remainder was infested pasture land and roadways 1/2 to 1 1/2 miles 
from the nearest crop. Ordinarily remote infestations are not considered 
an immediate threat to a crop. They are therefore overlooked and re- 
main a constant source of reinfestation. In these tests none of the in- 
festations, whether adjacent or remote, were permitted to enter the 
cotton. 

In the early spraying toxaphene was compared directly with aldrin. 
In three tests average nymphal populations of 40 to 49 per square.yard were 
reduced to zero by one application. Residual action of toxaphene was 
noted up to 4 days, after which there were no grasshoppers left. The 
killing action of the aldrin was a little faster than that of the toxaphene, 
for aldrin reduced similar infestations to 1 or less per square yard in 
3 days. 



-15- 



Both oil and emulsion sprays were used in the early aldrin and toxa- 
phene tests Nos. 4, 12, and 14. The oil sprays had to be applied with the 
USDA broadcast nozzle in calm weather, because they will drift with any 
appreciable wind. With the small quantity used per acre, drifting would 
reduce the dosage and the effectiveness of the spray. Emulsion sprays 
were applied with the side-delivery nozzle, often in windy weather since 
such weather was the rule. There was no difference in results between 
the oil and emulsion sprays regardless of the insecticide or type of 
vegetation. The oil spray at 1 1/4 gallons per acre did not seriously burn 
the vegetation. 

Dieldrin in the early spraying was applied on 103 acres at the average 
rate of 1.3 ounces per acre. Average populations of 25 to 49 grasshoppers 
per square yard were reduced to zero with one treatment. Some of the 
populations ran as high as 100 grasshoppers per square yard. For the 
first time cotton was sprayed directly to protect it from migrating fifth 
and sixth instars of differentialis . In central Texas this species goes 
through seven instars. Within 1 1/2 hours after the application there 
were many dead and dying grasshoppers and within 24 hours, all were 
dead. The dieldrin killed the grasshoppers faster than did either aldrin 
or toxaphene. 

In test No. 20 the grasshoppers were moving from a 15-acre cut hay- 
field into a 50 -acre cottonfield. The spraying of a barrier consisting of 
3 rods of weedy grass margin and 25 rows of cotton--5 acres altogether-- 
with 7 ounces of dieldrin wiped out the infestation in the barrier and all 
the grasshoppers moving in from the hayfield. 

North across the road, in test Nos. 21 and 22, a 34-acre cottonfield 
was threatened on the north by grasshoppers from a harvested 25-acre 
oatfield and on the east by those from cut hayfields. The spraying of 
37 acres of field margin, including 8 acres of cotton, with 56 ounces of 
dieldrin wiped out all infestations. On July 12 and 16 not a single grass- 
hopper could be found in the cotton, its margins, or adjacent oat stubble 
or hayfields. In contrast, a cottonfield to the north, not treated early, 
had 10 adult differentialis per square yard over most of it on July 13 
when it became test No. 24 in the late spraying. These results showed 
what early spraying could do. 

The 23 tests made with aldrin, dieldrin, and toxaphene gave excellent 
control of grasshoppers in all stages of nymphal development from May 3 
through June 18, or over a period of 47 days. All the worst infestations 
were reduced to practically zero. Maximum daily temperatures reached 
95 and 100° F. on a few days, but there was no long period of hot, dry 
weather. Sufficient rain fell to keep the vegetation green. On June 20 
operations were discontinued to await hotter and drier weather and adult 
infestations. 



• -16- 

Results of Late Spraying 

On July 6 a roadway and margin of a cottonfield were sprayed by the 
farm staff to protect the cotton from grasshopper damage, test No. 26, 
table 2 and figure 2. Aldrin in an emulsion spray was applied at the 
rate of 2 ounces of aldrin per acre on 17 acres of infestation numbering 
25 grasshoppers per square yard. Only a 60-percent reduction in pop- 
ulation was estimated after 4 days. This reduction was the first of the 
definitely poor results obtained with the dosages used earlier in the 
season. Two more treatments at 4.9 and 6 ounces per acre on July 14 
and 17, respectively, were required to reduce this infestation to 1 grass- 
hopper per square yard. 

On July 13, test No. 25, in bone-dry sunflower weeds, head high, 2 
ounces of aldrin per acre reduced a grasshopper population of 15 per 
square yard only 20 percent. A second application on July 16 at 8 ounces 
per acre reduced it to 1 or less per square yard. 

In remote native weedy pasture, where there was still some green 
foliage, 3 and 6 ounces of aldrin per acre in an oil spray (test No. 29) 
reduced a population of 12 grasshoppers per square yard to 1 and 1 or 
less per square yard, respectively. In this test Boopedon gracile was 
the dominant species and was the first to disappear after the treatment. 
It showed a greater susceptibility to the poison than the other important 
species, which were differential is , Hespereotettix viridis, H_. speciosus , 
and Phoetaliotes nebrascensis . 

In test No. 24, 1 ounce of dieldrin failed to give good results. An 
average dosage of 2.8 ounces per acre was required to secure the same 
results that an average of 1.3 ounces gave in early spraying. 

In test No. 27 toxaphene at 1 1/2 pounds per acre reduced an infesta- 
tion of 8 grasshoppers per square yard in cotton to 3 grasshoppers and 
at 3 pounds per acre reduced to 1 or less an infestation of 7 grass- 
hoppers per square yard in Johnsongrass. 

None of these insecticides were given a thorough study under hot, 
dry conditions because of the lack of infestation. Nevertheless, the 
results of the late spraying showed that there was a break-down in their 
effectiveness and that the break-down could be overcome by doubling, 
tripling, or quadrupling the dosages used in the early spraying. 

THE EFFECT OF WEATHER ON CONTROL OF 
GRASSHOPPERS WITH ALDRIN SPRAYS 

The failure of aldrin sprays in hot, dry weather in Texas in 1951 
called for a study of the causal factors. The most obvious factor was 
the weather itself. Similar failures had been experienced in North 
Dakota in 1950 under cold, wet conditions. 



-17- 



When the effect of weather on the results of spray operations was 
analyzed, temperature and rainfall were given the most serious con- 
sideration. 

Figure 3 shows the 1950 hatching curves for mexicanus and bivittatus 



in North Dakota and the 1951 curve for differentialis in Texas, plotted 
from the data gathered during the season's work in each area. The mean 
daily maximum air temperature and total rainfall for each 5-day period 
are shown in the form of a curve and a histogram for the season's work. 
The minimum effective hatching temperature of 60° F., below which no 
hatching takes place, and the temperature range of maximum grass- 
hopper activity, 80° to 90° F., are also given. 

In Bottineau County in 1950 cold, wet weather predominated, with 
daily maximum air temperatures mostly between 60° and 70° F. up to 
July 24. Spraying operations were begun on June 20, but adverse weather 
generally reduced the effectiveness of the sprays until July 24, when 
warmer weather set in with daily maximum temperatures above 80°. 
Occasional warm, clear days made it possible to get some good results 
in the first part of July, but most of the farm -scale spraying was done 
after July 24. From then on through August good results were obtained 
by selecting the best days for spraying. 

In North Dakota 90 percent of the mexicanus and bivittatus grass- 
hoppers had not hatched until the middle of July. There were no con- 
tinuous hatching temperatures until after May 20. In other work it has 
been demonstrated that in the spring the number of degrees each day 
the maximum air temperature is above 60° F. has to total 150 to 200 
before either species will start hatching. In Bottineau County in 1950 
this total was 163 degrees by May 31 and 200 by June 5. The hatching 
curves for both begin close to these dates. 

In Texas differentialis began to hatch about April 10. The number 
of degrees each daily maximum air temperature is above 60° F. has 
to total 600 to 700 before this species begins hatching. This total was 
627 degrees by April 1 and 786 degrees by April 10. Ninety percent of 
the grasshoppers had hatched by May 13. 

Good control of the grasshoppers in Texas was obtained with the 
sprays from May 3 to June 19, when daily maximum air temperatures 
in the 80 's predominated. Wind and rain during this period interfered 
with spraying operations, but did not affect the results. 

Poor kill of the grasshoppers was obtained when spraying was 
resumed on July 6 and in tests made from July 13 to 17. During this 
time there was no rain, the vegetation dried up, and maximum air 
temperatures above 95° or 100° F. were of daily occurrence. 

Grasshopper control with insecticides was poor in North Dakota 
when maximum air temperatures below 80° F. predominated and in 
Texas when they were above 95°. Above or below 80° and 90° F. there 
is a decrease in activity until at temperatures above 100° or below 70 
there is practically no voluntary activity on the part of the grasshoppers. 



- 18 - 



A poison generally becomes more effective as the activity of the 
insect increases. It is quite probable that the inactivity of the grass- 
hoppers at the low temperatures in North Dakota and at the high tem- 
peratures in Texas checked the toxic action of the aldrin sprays at the 
low dosages used. 

In Texas greatly increased dosages of the insecticides during the 
hot, dry weather gave good results, probably by increasing their con- 
tact or fumigating effect. They also increased the chance of an individual 
grasshopper getting a lethal dose during a period of inactivity and desultory 
feeding. 

In North Dakota the seasonal histories of both mexicanus and bivittatus 
vary from year to year. Ninety percent of these grasshoppers will hatch 
by May 15 one year and not until July 20 another year. It has been found 
that daily maximum air temperatures in the spring are closely correlated 
with the hatching period and that 60 to 80 percent of the variation in this 
period is associated with a year-to-year variation in these temperatures. 

In North Dakota sprays for grasshopper control are usually effective 
throughout July and August and into September without dosages being 
increased because temperatures seldom reach 95° to 100° F. Low tem- 
peratures in the season, however, are likely to reduce control appreciably. 
The proper timing of spray operations in relation to temperature is there- 
fore essential to efficient control operations. 

In Texas all of May and part of June can be utilized for spraying 
operations if daily maximum temperatures of 95° to 100° F. are not too 
common. This period should allow ample time for locating and controlling 
this species without the necessity of late spraying. 

If for any reason it does become necessary to protect a cottonfield 
from grasshopper damage during hot, dry weather, apply 4 to 8 ounces 
of aldrin, 2 to 3 ounces of dieldrin, or 3 to 4 pounds of toxaphene per 
acre as a money-saving measure. The 1946 yield of cotton in Texas 
was 130 pounds per acre and the farm price was 33.7 cents per pound, 
making cotton a cash crop of $43. 81 per acre for that year. With the 
price of aldrin 20 cents and of dieldrin 40 cents per ounce, and of toxa- 
phene 50 to 75 cents per pound, and the cost of aerial application $1 
per acre, spraying would be well worth while. Moreover, in most cases 
less than half the cottonfield requires spraying to protect the whole of it. 

Caution. --Do not feed crops contaminated with any of these insecti- 
cides to dairy animals, to animals being finished for slaughter, or to 
poultry. 



LEGEND 



-19- 



!«. 



■B JO 



utldings 



I* '• •*! Areas -Sprayed 

E$S^ Fallow Strips On stubble or one - 

woyed of trie time of .spraying) 
I - I Planted Strips mostly Smoll groins 
^ Shelter Belts 

Section Lines 

Half .Section Lines,! ences, and 

Field Margins. 

Graveled Roads 
(7) Section Numbers 

N 



J ' * 'Posture • • -JJJ §9" 
i-.'.'.'.'.'.W'.^-jfBamyard \ 

"ni F/ox S3* •Pa*K«ne-< 



Pasfure 



S3- 



"I 

■:::?< 

••.-.I 

--h, 

-1/2 mile 



P. • • -Alfalfa 

j-.-.-.v/. 

lOl 



Cropland 



(% 



I mile 




Figure 1. --Westhope (Sec. 31, upper right), and Maxbass (Sees. 12, 7, 13, 
and 18, lower part), N. Dak., areas, showing parts sprayed with aldrin 
for the control of grasshoppers in 1950. 



-20- 




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